(1) Field of the Invention
The present invention relates to an article inspection apparatus, and more particularly to an article inspection apparatus for sorting out articles that cannot be distinguished by appearance, based on different materials thereof or different net weights thereof.
(2) Description of the Related Art
It has heretofore been the customary practice to inspect articles that have been manufactured to ascertain whether they are defective or not. Primarily, products have been sorted out by determining if their appearance suffers deformation, damage, cracks, etc., or if any contents thereof have been filled up to a required level. Depending on whether products are to be sorted out on the basis of their appearance or contents, there have been employed various inspection processes.
Optical inspection processes have been employed in order to sort out articles according to their appearance. For example, a light beam or a laser beam is applied to an article, and a beam reflected or blocked by the article is detected. The reflected or blocked beam is processed by an image processing technique to recognize the shape or size of the article. The recognized shape or size of the article is compared with a reference shape pattern to determine whether the article is defective or not. If the recognized shape or size of the article is different from the reference shape pattern, then the article is judged as a defective article. According to another optical inspection process, the reflectance of a beam reflected from an article is measured, and the article is analyzed and sorted out on the basis of the measured reflectance.
To inspect an article for its content, there have been employed diagnostic processes for passing an X-ray or an ultrasonic wave through the article. The content of an article is determined according to the results of such a diagnostic process, and the determined content is used to sort out the article.
Empty can retrievers need to sort out empty cans according to their materials because they look exactly alike but are made of different materials such as aluminum and iron. Generally, an inspection process using a magnet is employed to sort out aluminum and iron cans. Another inspection process for sorting out aluminum and iron cans relies upon different load currents of an electric motor that is used to crush the aluminum and iron cans, as disclosed in Japanese patent publication No. 7-89388.
The image processing technique for recognizing article shapes is generally time-consuming for recognition processing. For example, inspecting a glass article for flaws on its surface requires a long inspection time as the entire surface needs to be inspected. Some articles cannot be inspected for their contents by the X-ray or ultrasonic diagnostic process. For example, the X-ray or ultrasonic diagnostic process cannot be used to inspect articles whose contents will be modified or adversely affected by being irradiated with X-rays or ultrasonic energy, and baked articles such as sintered bricks for minute internal pores contained therein.